1. Field of the Invention
The present invention relates to a touch sensing device and a touchscreen device capable of effectively removing noise introduced into a touchscreen panel.
2. Description of the Related Art
In general, a touch sensing device such as a touchscreen, a touch pad, or the like, an input means attached to a display apparatus to provide an intuitive input method to a user, has recently been widely used in various electronic devices such as cellular phones, personal digital assistants (PDAs), navigation devices, and the like. Particularly, as the demand for smartphones has recently increased, the use of a touchscreen as a touch sensing device capable of providing various input methods in a limited form factor has correspondingly increased.
Touchscreens used in portable devices may mainly be divided into resistive type touchscreens and capacitive type touchscreens according to a method of sensing a touch input implemented therein. Here, the capacitive type touchscreen has advantages in that it has a relatively long lifespan and various input methods and gestures may be easily used therewith, such that the use thereof has increased. Particularly, capacitive type touchscreens may more easily allow for a multi-touch interface as compared with resistive type touchscreens, such that they are widely used in devices such as smartphones, and the like.
Capacitive type touchscreens include a plurality of electrodes having a predetermined pattern and defining a plurality of nodes in which capacitance changes are generated by a touch input. In the plurality of nodes distributed on a two-dimensional plane, a self-capacitance or mutual-capacitance change is generated by the touch input. A coordinate of the touch input may be calculated by applying a weighted average method, or the like, to the capacitance change generated in the plurality of nodes. In order to accurately calculate the coordinate of the touch input, a technology capable of accurately sensing the capacitance change generated by the touch input is required. However, in the case in which electrical noise is generated in a wireless communications module, a display apparatus, or the like, a capacitance change may be hindered from being accurately sensed.
In the following Related Art Document (Patent Document 1), which relates to an integrating circuit in which an inverting integrating circuit and a non-inverting integrating circuit are combined with each other, two operational amplifiers are connected to each of a plurality of electrodes, such that volumes and areas thereof are increased. Further, in Patent Document 1, signals having opposite phases are applied to inverting terminals of two operational amplifiers, respectively, in order to remove noise. However, in the case in which a frequency of the noise is the equivalent of or a multiple of an operation frequency, the noise may not be effectively removed.